1 Answer
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HTTP 302 redirect to URL of the user's profile picture (use ?type=square | small | normal | large to request a different photo).

So what you get is not the typical JSON response, but the picture itself (via the HTTP redirect). You can try that by entering the graph API call into your browser location bar. For example, to see the profile pic of Mark Zuckerberg, try:
http://graph.facebook.com/markzuckerberg/picture